Buddypress theme showing up blank

I have just installed Buddypress and went to view the the site and showed the default wordpress theme. I then switched the theme to the buddypress default theme (making sure it was activated in both places) and the site is just a blank page.

Thanks for getting back to me. I had initially installed a pack option (supplied by my hosting service) which installed both wordpress mu and buddy press but did not install properly me thinks. So I installed the wordpress mu and then the buddypress plugin. Now templates working fine except I cant seem to get the default buddypress template and the Avenue K9 one seems to be broken (have downloaded and installed many times…no luck). So where can I find the defualt template to install…cause it doesn’t come up in the theme search (nor does Avenue K9)